How Membranes May Have Directed the Chemistry of Life’s Origin on Earth
One of the most profound mysteries in science is understanding how life first arose from the inanimate chemicals on the early Earth. Central to this question is the distinction between a mere chemical reaction in the environment and a living, self-sustaining cell. A defining feature of all living cells is the membrane that encloses and protects them, regulating the flow of molecules in and out. New research now illuminates the possibility that membranes themselves played a pivotal role not just as physical barriers but as selective sieves, influencing the very molecular handedness—chirality—that life universally employs today.
Biological chirality refers to the “handedness” of molecules, a property where substances can exist in two mirror-image forms much like left and right hands. Although chemically identical, these forms are not superimposable, leading to significant differences in how they interact biologically. For instance, all sugars incorporated into the backbone of DNA and RNA are exclusively right-handed, while amino acids used in proteins are left-handed. This universal chirality has baffled scientists for decades, prompting questions about why life settled on one “hand” over another.
The researchers approached this enigma by examining the role of primitive membranes analogous to those found in archaea — a domain of single-celled organisms known for their unique and robust membrane structures. These membranes differ chemically from bacterial membranes and likely resemble those of Earth’s earliest cells. The team created artificial membranes simulating archaeal properties and also developed hybrid membranes combining archaeal and bacterial characteristics to test how they selectively allowed molecules to pass through.
Their results revealed a striking preference: membranes mimicking archaeal structures showed higher permeability for right-handed sugars—the exact type found in DNA and RNA—while hindering their left-handed counterparts. This selective permeability suggests that these early membranes could have acted as physical filters, biasing the molecular components available inside nascent cells toward the chirality we observe universally in life today.
Notably, with amino acids, the researchers observed a more complex picture. Some left-handed amino acids, including alanine, which is hypothesized to be one of the earliest amino acids utilized by life, demonstrated an increased ability to permeate membranes with mixed bacterial-archaeal properties. This partial permeability aligns intriguingly with the biochemical diversity seen in contemporary organisms and highlights that membrane properties alone may not fully explain amino acid selection but certainly contributed significantly.
This line of inquiry opens a compelling avenue: the earliest cell membranes, far from passive boundaries, might have exerted selective pressure at the molecular level. By favoring molecules of certain chirality, these membranes could have set the foundational biochemical asymmetry essential for self-replicating nucleic acids and functional proteins—a cornerstone of life as we know it.
Moreover, the membranes studied are experimental proxies and only approximations of what the earliest membranes might have been. This caveat leaves open the possibility that primordial membranes harbored additional, yet undiscovered, characteristics influencing molecular passage. Future investigations may reveal more nuanced membrane features further shaping biochemical evolution.
This work bridges a critical gap connecting structural cell biology with astrobiology and the origins of life. Understanding how membrane properties influenced molecular selection helps explain why life universally uses one stereochemical orientation, a question that has long eluded definitive answers.
The authors emphasize that their experiments demonstrate membranes’ active role as stereochemical selectors—“sieves” that facilitate the passage of molecules matching the chirality of life. This mechanistic insight not only deepens our understanding of life’s emergence on Earth but holds implications for seeking life beyond our planet, where alternative biochemical pathways might be ruled out or favored by membrane-like structures.
This study employed an observational approach combining synthetic biology, biophysical chemistry, and molecular simulations to analyze passage rates of various chiral molecules through model membranes. Such interdisciplinary methodologies are vital for recreating and understanding prebiotic conditions impossible to observe directly from Earth’s distant past.
Furthermore, the differential permeability effects observed underscore the profound influence that even modest variations in membrane composition can have on molecular traffic. Such selectivity may have incrementally driven prebiotic chemistry toward complexity and the emergence of living systems capable of information storage and metabolic function.
In conclusion, the research presents a paradigm shift, reimagining early cellular membranes not simply as passive containers but as active participants in life’s origin. These structures appear to have conferred an essential chemical bias, favoring molecular handedness fundamental to the replication and function of biological macromolecules.
As studies continue to dissect the molecular nature of primordial life, the role of membrane selectivity offers a promising framework for understanding the earliest steps from chemistry to biology, a transition that remains one of the grandest scientific frontiers.
Subject of Research: Cells
Article Title: Permeability selection of biologically relevant membranes matches the stereochemistry of life on Earth
Web References: http://dx.doi.org/10.1371/journal.pbio.3003155
References: Goode O, Łapińska U, Morimoto J, Glover G, Milner DS, Santoro AE, et al. (2025) Permeability selection of biologically relevant membranes matches the stereochemistry of life on Earth. PLoS Biol 23(5): e3003155.
Image Credits: Goode O, et al., 2025, PLOS Biology, CC-BY 4.0
Keywords: origin of life, membrane permeability, chirality, stereochemistry, archaea, amino acids, nucleic acids, prebiotic chemistry
